Urbanization and industrialization cause air pollution in megacities, especially in emerging markets. For purifying the air to improve air quality, air treatment devices are widely used in homes, offices and automobiles.
An air quality indicator is usually integrated in the air treatment device to give the user an indication of the air quality. In this manner, the air treatment device may further comprise an air sensor and a processor. The air sensor measures the air quality and provides a measurement output, and then the processor reads the measurement output of the air sensor and controls the air quality indicator to give an indication to the user based on the measurement output of the air sensor. However, the measurement output of the air sensor may drift over time, and the air sensor itself may also show inconsistencies between measurements, even in the same batch, as a result of which the air quality indicator may give a wrong indication to the user; consequently, it is hard for the user to check whether the indoor air quality has really improved, which is annoying and may reduce people's confidence in the air treatment device.